A lithium mixed metal oxide has been used as a positive electrode active material for a nonaqueous electrolyte secondary battery such as a lithium secondary battery. The lithium secondary battery has already been put into practical use as a small-sized power supply for use in portable telephones, notebook personal computers, etc., and has also been tried to be applied to a middle-sized to large-sized power supply for use in automobiles, power storage, etc.
As a conventional lithium mixed metal oxide, Patent Document 1 has specifically disclosed Li(Mn0.1Ni0.45Fe0.45)O2.